INTERNET-DRAFT J. Loughney Internet Engineering Task Force Nokia Issued: 14 July 2000 Expires: 14 January 2001 The Use of ENUM Services by Signaling Transport Protocols Status of This Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as 'work in progress.' The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html . This draft is an individual contribution. Comments should be directed to the Author. This draft expires on 14 January 2001 Abstract This draft proposes to use ENUM resolution to support signaling transport. This draft outlines the resolution E.164 numbers by NAPTR in DNS to a service location. Considerations need to be made for scalability, reliability and performance. Internet Draft Use of ENUM Services by SIGTRAN Protocols July 14, 2000 Abstract...............................................................1 1 Introduction.........................................................3 1.1 Scope ............................................................3 1.2 Terminology ......................................................3 1.3 Signaling Transport Overview .....................................3 2 Overview.............................................................3 3 Formats..............................................................4 3.1 Using DNS for Storage of E.164 Numbers ...........................4 3.2 NAPTR RR Format ..................................................4 3.3 Lookup Format ....................................................4 4 Examples.............................................................5 5 Security Considerations..............................................5 6 IANA Considerations..................................................5 7 Acknowledgments......................................................5 8 Author's Addresses...................................................5 9 References...........................................................5 Full Copyright Statement...............................................6 Loughney [Page 2] Internet Draft Use of ENUM Services by SIGTRAN Protocols July 14, 2000 1 Introduction This document proposes a new service, called 'sig' to enable ENUM resolution of E.164 numbers for the purpose of signaling transport. By querying DNS for signaling transport options of a particular network entity assigned a E.164 number, signaling transport protocols can locate the network entity within an IP network. 1.1 Scope This document introduces a new service into DNS. How the network entities are provisioned by operators and service providers is outside of the scope of this document. This document puts no requirements on the signaling transport protocols themselves. 1.2 Terminology ENUM - Telephone Number Mapping GT - SS7 Global Title GTT - Global Title Translation IUA - ISDN Q.921-User Adaptation M2UA - MTP2 User Adaptation M3UA - MTP3 User Adaptation SIGTRAN - Signaling Transport SCTP - Stream Control Transport Protocol SRV RR - Service Resource Record SS7 - Signaling System No. 7 SUA - SCCP User Adaptation UA - User Adaptation URI - Uniform Resource Identifier 1.3 Signaling Transport Overview The Framework Architecture for Signaling Transport [RFC 2719] defines a framework for transporting SS7 Application Protocols (SS7 AP) over IP. Current solutions call for a transport protocol, SCTP [SCTP] as the signaling bearer, with a number of User Adaptation layers [IUA] [M2UA] [M3UA] [SUA]. The User Adaptation (UA) layer will carry an SS7 AP between two IP nodes. This UA may need to perform some address translation (from an SS7 address to IP address) in order to setup a signaling bearer between the IP endpoints. 2 Overview Telecom services and networks are migrating to IP. This introduces some complications for address resolution, since upper layer protocols may use SS7 addressing schemes, while using IP addresses Loughney [Page 3] Internet Draft Use of ENUM Services by SIGTRAN Protocols July 14, 2000 for transport. Certain Application Protocols may carry addressing to be used as the SS7 Global Titles, which will need to be resolved to URIs. For Application Protocols that use E.164 numbering plans, we can define a service so that ENUM can be used to retrieve the corresponding Resource Record associated with the element. From there, the next step will involve using NAPTRs to find the service location of the needed signaling protocol. Finally, the last step is the sending of a "sig" related application message using a specific protocol (e.g., TCP or SCTP) to the cellular network element corresponding to the domain name in the Target field of the retrieved SRV RR. This assumes a public IP network. If the network elements always use E.164 numbers in the GT for the subsequent messages, it may be worthwhile to add IP address / host name as another option for the service entity as an enhancements to a SS7 Application Protocol, but that is outside of the scope of this document. 3 Formats 3.1 Using DNS for Storage of E.164 Numbers The rules for storing an E.164 number in DNS are described in [E.164- DNS]. A quick overview is: Take a full E.164 number (including country & city codes), remove all non-digit characters. Insert a dot (i.e. - '.') between all the digits. Reverse the order of the digits. Append the .e164.arpa domain to the end. This is the DNS name of the E.164 number. For example: +358-60-111-2222 becomes 2.2.2.2.1.1.1.0.6.8.5.3.e164.arpa. This is the host name where the sig RRs can be found. 3.2 NAPTR RR Format Following the format given in [NAPTR], were the DNS record is defined by the statement: ;; order pref flags serv regexp replacement IN NAPTR 100 10 "" "" "/urn:cid:.+@([^\.]+\.)(.*)$/\2/i" . The service field should be filled in with "_sig+E2I" for support of the sig service. 3.3 Lookup Format If a client wants to discover the location of the server providing the sig service, using a particular transport protocol (for example TCP, SCTP) it should do a lookup of: x.x.x.e164.arpa Loughney [Page 4] Internet Draft Use of ENUM Services by SIGTRAN Protocols July 14, 2000 where x.x.x is the processed E.164 number returned by step 1 on the ENUM service. 4 Examples This example shows how the 'sig' service could be used. This is only an example - any resemblance to any existing services or domains (living or dead) is purely coincidental. $ORIGIN 2.2.2.2.1.1.1.0.6.8.5.3.e164.arpa. IN NAPTR 10 10 "s" "sig._sua+E2I" "" _sua._sctp.nokia.com IN NAPTR 10 10 "s" "sig._m3ua+E2I" "" _m3ua._sctp.nokia.com IN NAPTR 10 10 "s" "sig._m2ua+E2I" "" _m2ua._sctp.nokia.com and then _sua._sctp.nokia.com would return: ;; Pref Weight Port Target _sua1._sctp.nokia.com IN SRV 0 0 1000 glc1.nokia.com IN SRV 0 0 1000 glc2.nokia.com IN SRV 0 0 1000 glc3.nokia.com 5 Security Considerations As this service is built on top of DNS, the results from any query will not be more secure than any other DNS query. DNSSEC therefore, is strongly recommended for securing and verifying zones. 6 IANA Considerations The E2I service has not been standardized yet. It has been suggested to setup a IANA registry for NAPTR. It may also be worthwhile to register the sig service with IANA. 7 Acknowledgments The author would like to thank Michael Mealling, Patrik Falstom for their illustrative examples on the ENUM mailing list. The author would also like to thank James Yu for input in a related draft. 8 Author's Addresses John Loughney Nokia Research Center PO Box 407 FIN-00045 Nokia Group Finland john.loughney@nokia.com 9 References [ENUM-REQ] "ENUM Requirements" , December 1999, Work in Progress. [E.164-DNS] "E.164 number and DNS" , July 10, 2000, Work In Progress. Loughney [Page 5] Internet Draft Use of ENUM Services by SIGTRAN Protocols July 14, 2000 [ENUM-OP] "ENUM Service Specific Provisioning: Principles of Operation", , April 2000, Work in Progress. [IUA] Kalla, Malleswar, et al., " ISDN Q.921-User Adaptation Layer"; ; June 2000; Work in Progress. [M2UA] Morneault, et al.; "SS7 MTP2-User Adaptation Layer"; ; December 1999; Work in Progress. [M3UA] Sidebottom, et al.; "MTP3-User Adaptation Layer" , March 2000, Work in Progress. [NAPTR] Mealling, M.; Daniel R. "The Naming Authority Pointer (NAPTR) DNS Resource Record"; ; June 24, 1999; Work in Progress. [RFC 2719] Ong, et al.; RFC 2719, "Framework Architecture for Signaling Transport" October 1999. [SCTP] Stewart, et al.; RFC XXXX, "Stream Control Transport Protocol", July 2000. [SUA] Loughney, et al.; "SS7 SCCP User Adaptation Layer"; ; July 2000; Work in Progress. [RFC 2782] Gulbrandsen, Vixie and Esibov, "A DNS RR for specifying the location of services (DNS SRV)" RFC 2782, February 2000. [RFC 1034] Mockapetris, P., "Domain names - concepts and Facilities", STD 13, RFC 1034, November 1987. Full Copyright Statement Copyright (C) The Internet Society (2000). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. Loughney [Page 6] Internet Draft Use of ENUM Services by SIGTRAN Protocols July 14, 2000 This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. This draft expires on 14 January 2001 Loughney [Page 7]